Apparatus of catalytic gasification for refined biomass fuel at low temperature and the method thereof

ABSTRACT

Disclosed is a gasification technique for converting biomass, which is difficult to treat, into clean gas fuel able to be burned in a cogeneration system. The gasification technique includes first stage fluidized-bed catalytic gasification, and second stage gasification of tar and catalytic reforming to convert nitrogen in tar, and HCN in a flammable gas into NH 3 , unlike conventional gasification techniques. In addition, since the temperature of a total gasification process is lower than a melting point of ash, powdery ash is generated and thus easily treated. Also, little heat is released due to the low process temperature, and therefore, a compact reactor may be designed to produce gas having a high caloric value. Further, the generated tar is recovered and reused in other processes, and the gas fuel contains a small amount of ammonia.

TECHNICAL FIELD

The present invention relates, in general, to gasification techniquesfor using biomass having a low inorganic ash content and a high nitrogencontent as clean fuel in a local heating system of a big city.

In particular, the present invention relates to an apparatus and methodfor manufacturing a gas fuel via clean gasification of a selectivelyrefined mixture (SOCA: Sludge-Oil-Coal Agglomerates) comprising biomassorganic waste, heavy oil, and coal.

As such, the gas fuel obtained after clean gasification is a clean gasfuel usable in gas combustors, such as gas engines, gas turbines, vaporturbine generators, fuel cells, boilers, etc., or in heating devices. Inaddition, the biomass is organic solid materials, which includeindustrial waste such as sewage sludge, pulp sludge, etc., living wastesuch as home waste, excretions, etc., agricultural waste, livestockexcretions, or wood chips.

BACKGROUND ART

Generally, gasification techniques have begun to be used to easilyprepare gas fuel or synthetic gas from coal in the absence of acatalyst. In recent years, the above techniques have been developedtoward entrained gasification and catalytic gasification for fine coal.

While fluidized-bed catalytic gasification, which is combined withfluidized-bed combustion techniques, has been applied to heavy oilreforming, and has been attempted for use in gasification of coal andbiomass, methods for high-temperature and clean gasification to producea minimum of tar are being devised.

Solid fuel is gasified along with reactive materials, such as air,oxygen, or steam, and thus, is converted into a flammable gas, condensedliquid/tar, and solid residue. Generally, although gasification is usedto maximally convert solid fuel into gas fuel, it may be limitedlyapplied in a partial gasification process. In addition, pyrolysis, whichis different from gasification, means thermal decomposition of solids inan inert atmosphere. However, the initial state of gasification isassumed to be devolatilization of pyrolysis. At this time, the fuel isdecomposed into char and volatile components. After thedevolatilization, a final component distribution of product gas isdetermined through the secondary reaction between char and volatile gas.In practice, the distribution of the product varies greatly with thegasification methods and the process conditions.

In high-temperature gasification, almost all inorganic materialcontained in coal or sludge is converted into ash or slag. In addition,iron or sodium contained in coal or sludge is volatilized at 900° C. orhigher, and then sticks on the wall of a heat exchanger. In addition,fuel-nitrogen (fuel-N) is converted into NH₃, HCN, or N₂, viagasification, in which the conversion depends on the type ofgasification reactor, fuel properties and operation conditions.

Since the gasification of coal is typically performed at a hightemperature, it requires a lot of energy. The gas thus obtained has alow caloric value, and ashes enter a molten state. Consequently, thesystem is too large or is complicated. However, when a catalyst able toimprove gas composition and operation conditions is used, a gascomposition the same as is obtained upon high-temperature gasificationin the absence of a catalyst is obtained even at a relatively lowtemperature, and the conversion of fuel-N is easier. According to somereports, the conversion of fuel-N into NH₃ and HCN is affected by thecatalyst and reaction temperature. That is, fuel-N is readily convertedinto NH₃ in the presence of Fe and Ni catalysts at 900° C. or more,while HCN is readily obtained in the presence of a dolomite catalyst at800° C. or more.

A gas resulting from gasification typically has a low caloric value. Forexample, compared to LNG having a caloric value of about 10,000kcal/Nm³, a gas having a low caloric value of 1,100-1,450 kcal/Nm³ isobtained when gasifying coal having a caloric value of 6,850 kcal/kg.

The low-temperature non-catalytic gasification of coal is, in practice,performed at a temperature of not less than a melting point of ash, dueto a low conversion rate. However, since the gasification of biomasshaving lower ash content adopts catalytic gasification, fuel having highquality may be obtained while decreasing the conversion of fuel-N intoNO at a low temperature at which ash slagging does not occur.

Further, the above process is applied to gasification of waste having ahigh caloric value or heavy oil, or to a fuel mixture containing coal.Particularly, waste containing chlorine ion is designed to have aretention time of 2 sec or more at 1200° C. or higher to remove it ordirectly burn it after gasification. In addition, in the case of polymerwaste having high quality, a specific gasification process, whichproduces a fuel having high quality, such as hydrogen, may be proposed.

However, a specific gasification apparatus requires a means for removingand refining large amounts of impurities, such as ash included in a rawmaterial, and generally, also requires a quenching system to produceash, which is melted by increasing the temperature to achieve highgasification conversion in the absence of a catalyst, into fine slag.Further, a pure oxygen or air separating device for the production of agas having high caloric value is used, thereby increasing the drivingcost or mounting cost. For gasification of a raw material having a lowcaloric value, a system is installed for indirect heating particularlyby an external heat source and pyrolysis through supplying only steam tothe system, and is thus used for specific purposes when economy isunimportant.

Hence, the partial oxidation in the absence of a catalyst isdisadvantageous because high-temperature air or enriched oxygen must beused to achieve high-temperature gasification. Also, additional fuel isconsumed to obtain a product gas (CO and H₂) having high quality.Further, expensive heat resistant material suitable for high-temperaturereactions should be used, and also, the reactor has a short servicelife. Furthermore, about 2˜5% of the free carbon that is produced byhigh-temperature partial combustion using a fixed-bed reactor isdeposited, and the reaction efficiency is gradually decreased, thusrequiring additional cost for removing the deposited material.

In the clean solid fuel having less tar or char, circulatinglow-temperature catalytic gasification, in which organic hydrocarbon andwater vapor are converted into a product gas in the presence of an oxidecatalyst (MO), may be conducted. Therein, the catalyst is reduced andconverted into a pure metal (M). A metal (M) having decreased catalyticactivity is reproduced into metal oxide (MO) in a combustor. Inaddition, the catalytic reaction is conducted at a low temperature of400-600° C., and a liquid product may be produced in a very smallamount. However, the above gasification is limited to use for wastecontaining a higher ash content or catalytic poison.

The circulating reforming catalyst generally includes Ni and Co, andpreferably, V, Cr, Fe, Cu, Mo, Ag, Cd, La, Ce, or perovskite catalysts,and more preferably, a precious metal having high catalytic efficiency,such as Rh or Ru. In addition, such a catalyst may be affixed to asupport formed of oxides of at least two metals selected from among Mg,Ca, Sr, Ba, Al, Ce, Si, Ti, and Zr. However, since these catalysts havelow activities due to catalytic poison at a low temperature, they mayneed to undergo high-temperature reaction or reproduction to be stablyused. Consequently, free carbon is deposited on the catalyst, or reactswith the support to form another product. For example, an Ni catalystreacts at high temperature with alumina, to produce NiAl₂O₄, resultingin decreased catalytic activity. To avoid such a reaction, hexaaluminate(MeO.6Al₂O₃), which has high temperature resistance, may be used as asupporter.

Moreover, liquid waste containing large amounts of solid impurities,such as heavy metals, may be gasified in a supercritical state using areactor into which a catalyst is loaded. As such, the catalyst, such asRu, Pd, R, Pt, Au, Ir, Os, Fe, Ni, Ce, or Mn, may be impregnated intotitania or zirconia having high temperature resistance, and be driven at250˜600° C. under 5˜130 MPa. The catalyst used is expensive preciousmetal, and is thus recovered using a gas-liquid separator to be reused.

A solid-solid catalytic reaction is difficult to perform in practice.Hence, the catalytic gasification of coal, in which an alkali catalyticcomponent is impregnated into coal or a large amount of alkali metal inash is used, has been initially developed. However, in recent years, asthe char gasification reaction of coal was proven usually to be causedby fine volatilization on the surface of particles, attempts have beenmade to mix a solid catalyst with coal. In the case of sub-bituminouscoal having a relatively large amount of volatile material, potassiumcarbonate is used as a catalyst. As such, the solid material containedin the ash affects the gasification properties. On the whole, apotassium catalyst has a large difference in activity depending on thetype of anion combined therewith. In addition, the activity of an ironion is easily decreased by sulfur, and a nickel ion having low catalyticactivity due to catalytic poison restores the activity at a hightemperature at which the poisonous material is desorbed.

Using the catalytic properties, the gasification may be rapidlyconducted at a relatively low temperature of 700˜850° C. in the presenceof an optimal catalytic composition, such as K₂SO₄+FeSO₄,K₂SO₄+Ni(NO₃)₂, or K₂SO₄+CaCO₃. However, a complicated apparatus formelting the remaining ash is necessary due to its low conversion.

Of two-stage gasification methods, air gasification in a cylindricalreactor and water vapor gasification outside of the reactor areconducted at about 850° C., thus obtaining a gas product having a meancaloric value. Limestone is used as a catalyst, in consideration ofsulfur poisoning in coal. As such, the reaction is as follows:H₂S+CaO→CaS+H₂O

Then, the solid materials, for example, CaS, CaO and limestone, may beseparated from each other by use of the difference in density in thereactor. The ash and limestone may be separated from each other in thelower portion of the reactor. To this end, however, accurate driving isrequired due to a complicated reactor and process.

FIG. 1 is a view showing a conventional apparatus for two-stagegasification of biomass at a high temperature in the absence of acatalyst. In a conventional two-stage pyrolysis apparatus of biomassshown in this drawing, a biomass fuel is supplied to a circulatingfluidized-bed heating furnace 102 from a fuel hopper 101, and thensequentially passed through a cyclone 103, a char separator 104 and agas reforming furnace 105, to achieve two-stage pyrolysis. Subsequently,the fuel gas is passed through a pre-heater 106 and then a gas quencher107, whereby fly ash is collected in a collector 108 and a gas isrefined in a refiner 109.

The above apparatus is disadvantageous because first-stage pyrolysis isconducted at 450˜850° C., which is not high, in the absence of acatalyst, in consideration of high-temperature volatilization of heavymetal, thus obtaining a low gasification yield and generating excesstar. Hence, a process of reforming tar should be necessary to increasethe gasification yield, which is conducted at 1000˜1200° C. in theabsence of a catalyst. Although exhaust flue gas desulfurization isconsidered for biomass containing a low sulfur content, pollutionattributed to high content of phosphorous or fuel-N is not considered,causing secondary environmental pollution. In particular, the aboveapparatus has the gas quencher 107 for inhibiting the dioxin conversionby chlorine ions present in the raw material.

FIG. 2 is a view showing a conventional apparatus for two-stagecatalytic gasification of waste having high quality. Since the wastehaving low impurities with a high caloric value has a small amount ofpoisonous material, as shown in FIG. 2, a raw material undergoes firststage partial oxidation and pyrolysis using a fluidized-bed in theabsence of a catalyst at about 700˜800° C. in a fluidized-bed gasifier110, after which the temperature of the produced flammable gas isdecreased to about 300° C. Then, slaked lime is added to fix Cl and S,which are then collected in a cyclone 103 to remove them. Thetemperature of the flammable gas is increased again after passingthrough a gas mixer 111 and a combustor 112, and thereafter, secondstage tar catalytic reforming is conducted in a gas reformer 113. It isknown that an NiO/MoO catalyst is active at 400˜500° C., and a catalystobtained by supporting Ni, Cr and Fe to alumina is active at 800˜1000°C. The reference numeral 114 designates a boiler, and the referencenumeral 115 designates a gas-holder. Also, parts common to the apparatusshown in FIG. 1 have the same reference numerals.

DISCLOSURE OF THE INVENTION

Technical Tasks To Be Solved By The Invention

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a catalytic gasification technique ofpoison-resistance in a first stage gasification process using a furtherrefined fuel to increase the gasification yield at a low temperature,and then in the gasification of tar and conversion of tar-N and HCNpresent in a flammable gas into NH₃ in a second stage catalyticreforming process.

Another object of the present invention is to provide a gasificationtechnique, using a compact apparatus without the need for a molten ashquenching system, in which the unit calories of the produced gas areincreased and ash is formed not in a molten state but as fly ash, byminimizing the content of CO₂ in the gas while decreasing the energyconsumption of a reaction system by decreasing the temperature of atotal process.

Technical Solution

In order to accomplish the above objects, the present invention providesan apparatus for low-temperature catalytic gasification of a refinedbiomass fuel, comprising a fuel hopper to momentarily receive refinedfuel, and including a screw feeder to quantitatively feed the fuel,provided at the lower portion thereof; a catalytic circulatingfluidized-bed gasifier provided in the rear of the fuel hopper, andincluding a shutter connected to the screw feeder, provided at a middleportion of the gasifier, and a hot air pipe and a steam pipe, providedat a lower portion thereof; a dust collector connected to the catalyticcirculating fluidized-bed gasifier via a pipe extending from the upperportion of the catalytic circulating fluidized-bed gasifier to the sidewall of the upper portion of the dust collector, to collect fly ash; acatalyst reformer connected to the dust collector via a pipe extendingfrom the upper portion of the dust collector to the lower portion of thecatalyst reformer, and including a lower layer of fixed filter adsorbentbed and an upper layer of fluidized catalyst bed; a heat exchangerconnected to the catalyst reformer via a pipe extending from the upperportion of the catalyst reformer to the middle portion of the heatexchanger; a tar scrubber disposed in the rear of the heat exchanger,and including a tar scrubbing chamber, a tar-storing bath, and acirculation pump for circulating tar; and a gas-holder disposed in therear of the tar scrubber.

In addition, the present invention provides a method of low-temperaturecatalytic gasification of a refined biomass fuel, comprising a fuelsupplying step of supplying a refined mixture including biomass organicwaste, coal and heavy oil to the middle portion of a gasifier throughscrew feeder; a catalytic circulating fluidized-bed gasification step ofdrying, volatilizing, low-temperature catalytic gasifying, and partiallyburning the fuel using hot air and steam in the presence of a catalyst;a collecting step of collecting fly ash contained in the gas in theprevious step; a catalyst reforming step of reforming the gas through alower layer of filter and reforming tar-nitrogen, aromatic-nitrogen,phosphorous and sulfur through an upper layer; a heat exchanging step ofcooling the gas to 200° C. or less and transferring condensed liquid toa tar-storing bath; a tar scrubbing step of condensing non-converted taror non-condensed liquid to be recovered, and gas stripping the condensedliquid; and a gas-holding step of compressing the gas to be storedtemporarily.

Advantageous Effects

According to the present invention, the gasification of a fuel which isinitiated at a temperature lower than that of a single fuel material maybe conducted at a temperature which is further decreased by using acatalyst. Thereby, oxygen consumption required to maintain the operationtemperature is decreased, thus a desired fuel may be inexpensivelyproduced. In addition, since the operation temperature of a gasifier islow, little heat is released and a slagging treatment system is notneeded, thereby realizing a compact apparatus. In addition, a gasproduct obtained by using a smaller amount of air in the presentinvention has the same caloric value as a gas product resulting fromconventional gasification using oxygen, therefore generating economicbenefits.

The present invention pertains to clean energy producing techniques forconverting a highly refined mixture comprising sludge and coal into aninexpensive gas fuel having a high caloric value.

The gasification of the refined mixture comprising sludge/coal/oil isinitiated, along with a material having a high initiation temperature ofgasification, at a temperature lower than that of a single component.Thus, gasification may be performed for a short time, hence achievingrapid gasification. A low ash content and easy control of fly ash at alow temperature make it easier to decrease the size of an apparatus,leading to saved energy and efficient operation. Moreover, since a heavymetal and a salt are present in a very small amount, a combustionpost-treatment system is not needed.

The gasification adopts a fluidized-bed type which may be driven at arelatively low temperature. Thus, even if the gasification is conductedat 850° C. using inexpensive coarse limestone powders or particles whichenable gasification at a low temperature, it may exhibit the sameeffects as conventional gasification at 1100° C. or more in the absenceof a catalyst.

Conventionally, the reformation temperature of a tar reformer is in therange of 1200° C. or more, which is higher than a gasificationtemperature. However, in the present apparatus, the reformationtemperature is decreased to 650° C. or less, and thus, the reformer ofthe present invention does not need an additional heat source. Beforethe catalytic reformation, hydrogen sulfide and phosphorous pentoxidegas acting as a catalyst poison component are fixed to be removed by theuse of caustic lime, thus increasing the reformation of tar and theconversion of fuel-N into NH₃ in the presence of a catalyst.

Although tar, regarded as an unnecessary material, is re-circulated orwasted in a conventional process, in the present invention, unreactedtar, tar generated from the catalytic reformation, and a liquid productformed upon cooling the gas are recovered and then used for otherpurposes. Typically, additional devices or usage methods are required tore-introduce an undesired liquid component such as tar caused by aconventional coal gasification process into the gasification process orto use it as a liquid fuel. However, in the present invention, sincesuch a component may be used as an agglomerating agent to form anagglomerate, it is not problematic.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a conventional apparatus fortwo-stage gasification of biomass at a high temperature in the absenceof a catalyst;

FIG. 2 is a schematic view showing a conventional apparatus fortwo-stage catalytic gasification of waste having high quality;

FIG. 3 is a view showing an apparatus for two-stage catalyticgasification of a refined biomass fuel, according to the presentinvention;

FIG. 4 is a view showing the gasification properties of refined sewagesludge fuel in the absence of a catalyst and in the presence of acatalyst; and

FIG. 5 is a view showing the two-stage catalytic gasificationcharacteristics of refined sewage sludge fuel.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference should now be made to the drawings, in which the samereference numerals are used throughout the different drawings todesignate the same or similar components.

FIG. 3 is a view showing a catalytic gasification apparatus for use inrecovering an energy source in the form of gas from a refined biomassfuel, according to the present invention.

The refined biomass fuel, which is a flammable material obtained byselectively separating and recovering an organic solid component frombiomass and coal, along with oil, using an oil agglomeration or floatingprocess, has a non-flammable inorganic material (hereinafter, referredto as ‘ash’) present in an amount less than 6% based on dried material,and is a solid fuel having high quality with a caloric value of 7,000kcal/kg or more.

The apparatus of the present invention comprises a fuel hopper 10 forreceiving fuel, a screw feeder 11 to supply the received fuel to asubsequent device, and a catalytic circulating fluidized-bed gasifier 20provided in the rear of the fuel hopper 10.

The catalytic circulating fluidized-bed gasifier 20 includes a shutterprovided at a middle portion thereof and through which the fuel issupplied from the screw feeder 11.

In addition, the catalytic circulating fluidized-bed gasifier 20 has ahot air pipe 21 and a steam pipe 22 disposed in a conical lower portionthereof. As such, the hot air pipe 21 is positioned at the same level asthat of the conical lower portion, and the steam pipe 22 is positionedsuch that its end is protruded to a height of 15˜30 cm apart from thelower portion.

At the upper portion of the catalytic circulating fluidized-bed gasifier20, a small cyclone 23 may be further provided.

A dust collector 30 is provided in the rear of the catalytic circulatingfluidized-bed gasifier 20, and a pipe extending from the upper portionof the catalytic circulating fluidized-bed gasifier 20 is connected tothe side wall of the upper portion of the dust collector 30. The dustcollector 30 functions to collect fly ash in the gas in the lowerportion thereof. In addition, a catalyst reformer 40 is provided in therear of the dust collector 30, and a pipe 31 extending from the upperportion of the dust collector 30 is connected to the lower portion ofthe catalyst reformer 40.

The catalyst reformer 40 has a fixed filter adsorbent bed 41 disposed inthe lower portion thereof, and a fluidized catalyst bed 42 formed on thefixed filter adsorbent bed 41.

The fixed filter adsorbent bed 41, which is a cartridge type, mayinclude a mixture comprising an asbestos filter, particles of alkaliearth metal oxide and powdery particles of alkali metal salt.

The pipe 31 extending from the upper portion of the dust collector 30 isprovided with a valve 32 at an intermediate position thereof thatcommunicates with a steam pipe 33, and the pipe 31 communicates with asteam sprayer 43 disposed at the lower portion of the fixed filteradsorbent bed 41 of the catalyst reformer 40.

In order to prevent liquid from condensing in the gas pipe extendingfrom the cyclone 30 to the catalyst reformer 40, super-heated steam isfed into the gas pipe through the steam pipe 33 so that the gas pipedischarges the super-heated steam into the catalyst reformer 40 alongwith the gas to cause the remaining tar to be further gasificationreformed.

In addition, a heat exchanger 50 is provided in the rear of the catalystreformer 40. Also, a tar scrubber 60 is provided after the heatexchanger 50, and includes a tar scrubbing chamber 61, a tar-storingbath 62 disposed at the lower portion thereof, and a circulation pump 63for circulating tar. The tar-storing bath 62 communicates with a lowerpipe of each of the catalyst reformer 40 and the heat exchanger 50 viaindividual tar valves 64 to collect the generated tar from the catalyst40 and the heat exchanger 50.

Further, a gas-holder 70 is provided in the rear of the tar scrubber 60,and a fuel gas-storing pump 71 is disposed between the tar scrubber 60and the gas-holder 70.

Hereinafter, a method of manufacturing clean gas using the apparatus ofthe present invention is described.

A refined fuel mixture, which is supplied through a screw feeder 11 froma fuel hopper 10, undergoes drying, volatilization, low-temperaturecatalytic gasification, pyrolysis gasification and partial burning, byair or oxygen and water vapor fed via a hot air pipe 21 and a steam pipe22 in a catalytic circulating fluidized-bed gasifier 20. Unreacted fuelcomes into contact with air or oxygen at the conical lower end of thegasifier, and thus, is completely burned.

The ratio of air or oxygen supplied into the catalytic circulatingfluidized-bed gasifier 20 is about 0.3˜0.7 based on the amount of airrequired for theoretical complete combustion of the refined fuelmixture, and water vapor is fed at a volume ratio of 0.5˜10 times thatof air. The fluidized catalyst for gasification in the catalyticcirculating fluidized-bed gasifier 20 includes natural limestone, limemagnesite, or caustic lime, an alkali earth metal such as calcium,magnesium or barium and oxides thereof, an alkali metal such aspotassium and oxides thereof, alumina, or mixtures thereof, each ofwhich is provided in the form of particles or coarse powders suitablefor fluidization. By using the catalyst, the gasification is conductedat a maximal temperature of 900° C. or less by high-speed operation, forexample, for a gas retention time of 2˜4 sec.

Preferably, partial oxidation and low-temperature catalytic pyrolysisare simultaneously conducted at 850° C. or less. Upon partial oxidationfor feeding a heat source to a system, most gasification uses oxygen ata high temperature. However, in a novel process, even if a fuel havinghigh quality reacts with air serving as a fuel oxidant at a relativelylow temperature, the gas may be produced to have the same caloric valueas that of a conventional process using oxygen. As such, air is sprayedfrom the lowermost portion of the gasifier, whereby the lowermostportion of the gasifier has excessive oxygen for complete combustion ofunreacted flammable material.

In addition, a small cyclone 23 is provided to the upper portion of thecatalytic circulating fluidized-bed gasifier 20 to efficiently collectscattered catalyst or fuel agglomerate such as unreacted material andheavy tar, which is then re-circulated to the catalytic circulatingfluidized-bed gasifier 20, thus completing the gasification.

In the cyclone 30, a small amount of fly ash may be efficientlycollected and removed.

The catalyst reformer 40 has a two-layered structure, including a lowerlayer of cartridge type fixed filter adsorbent bed 41 and an upper layerof fluidized catalyst bed 42.

In the fixed filter adsorbent bed 41, fine fly ash is removed via anasbestos filter, and sulfur and phosphorous poisoning are chemicallyadsorbed and removed using potassium oxide and sodium carbonate as anadsorbent. Also, a detoxification filter may be recycled or replacedafter being used for a predetermined period. For example, hydrogensulfide (H₂S) generated upon gasification reacts with CaO and isconverted into CaS, which is then adsorbed. Also, a vapor compound suchas PH₄-halogen reacts with Na₂CO₃ to produce NaPO₃, which is thenchemically adsorbed. A phosphorous component is converted intoP_(α)H_(β)S_(γ)Halogen_(δ)(α=1-7, β=0-5, γ=0-7, δ=0-7) to be chemicallyadsorbed. Each of P_(x)S_(y) compounds, resulting from the gasification,reacts with a chemical adsorbent suitable therefor or a calcium salt tobe chemically adsorbed.

The fluidized catalyst of the fluidized catalyst bed 42 functions todecompose tar by gasification and convert aromatic nitrogen or HCN intoan alkane or alkene compound and NH₃. The usable reformation catalystincludes a single metal, such as Ni, Fe, Co, Mo, Mn, Zr, Ti, Ce, Ru, Rhor Pt, and oxides thereof, or mixtures thereof. Such a catalyst ispreferably used at 650° C. or less.

The heat of reformed gas is exchanged by using the heat exchanger 50 tocool the gas to 200° C. or less, and the condensed liquid is transferredin the tar-storing bath 62. As such, air or oxygen and water used in thegasification may serve as a cooling medium for heat exchange, and thenbe converted into hot air and steam. Moreover, the heat exchanger 50 mayincrease the energy efficiency if a metal heat exchanger made of ahigh-temperature material is used.

The non-converted tar or non-condensed liquid in the catalyst reformer40 is condensed in the tar scrubber 60, and then recovered in thetar-storing bath 62. In this case, to increase the recovery efficiencyof dust and tar, condensed liquid at 150° C. or less is re-transferredto the upper portion of the tar scrubber 60 through the tar circulatingpump 63, thus conducting gas stripping.

The resultant clean gas fuel is compressed and then stored temporarilyin the gas-holder 70.

A better understanding of the present invention may be obtained throughthe following examples which are set forth to illustrate, but are not tobe construed as the limit of the present invention.

Example 1 Improvement Of Gas Generation Efficiency BY CatalyticGasification

For gasification of SOCA (Sludge-Oil-Coal Agglomerates) in the presenceof a catalyst mixture comprising Fe₂O₃ and CaO, the catalyst mixture andSOCA were uniformly mixed at a weight ratio of 3.4:1 under operationconditions similar to gasification in the absence of a catalyst, thusobtaining a gas product. The state of the product is shown in FIG. 4.The gasification in the presence of the catalyst mixture was initiatedat 230° C., which was considerably lower than 560° C. required forgasification in the absence of a catalyst. In addition, compared togasification in the absence of a catalyst, CO conversion was lower, andmore hydrocarbons were generated. In particular, almost all hydrocarbonsgenerated were confirmed to be methane gas. In the gasification in theabsence of a catalyst, hydrocarbons were generated at 850° C. or more,and CO was generated at 1050° C. or more. However, when using a catalystmixture, CO and hydrocarbon were mainly generated at about 500° C.Further, CO was maximally generated at 850° C. Thereby, gasification wascompleted in a short time. After the gasification in the presence of thecatalyst mixture, unreacted char was present in an amount of about0.35%, which was superior to the about 11.31% char remaining afterconventional gasification at 1050° C. for 2 hr in the absence of acatalyst.

Example 2 Less Generation Of Tar and Fuel-N Pollutant By Two-StageCatalytic Gasification

As shown in FIG. 5, when a CaO catalyst, which is an oxide of an alkaliearth metal, was used in the first stage gasification and an NiOcatalyst was used in the second stage catalytic reformation, CO wassimilarly generated but a slightly larger amount of hydrocarbon wasgenerated, compared to gasification using only CaO as the first stagecatalyst Thereby, the reaction was completed in a shorter time. However,as is apparent from Table 1 below, in the case where calcium oxide wasused as a first stage catalyst and NiO or MnO₂ was used as a secondstage catalyst, the generation of tar, NH₃ and HCN was remarkably lowerthan when using only a first stage catalyst. It was considered that tarwas reformed and fuel-N was converted into N₂. In addition, the MnO₂catalyst was inferior in tar reformation to the NiO catalyst, by whichfuel-N was converted not into ammonia but into HCN. Thus, the NiOcatalyst exhibited superior fuel-N reformation performance as a secondcatalyst. TABLE 1 Conversion Of Tar and Fuel-N By Using Two-StageCatalysts Flammable Gas Composition After Conversion Tar NH₃ HCNGasification for 45 min (ppm) Catalyst (%) (%) (%) (%) CO CH₄ C₂H₄ C₂H₆C₃H₈ C₄H₁₀ 1^(st): CaO 99.08 3.385 0.889 0.656 14,805 209 12 76 2234,670 2^(nd): x 1^(st): CaO 99.90 0.123 0.278 0.045 14,429 305 4,9746,223 4,228 367 2^(nd): NiO 1^(st): CaO 99.84 0.703 0.465 0.164 15,76612,134 46 408 2,102 1,263 2^(nd): MnO₂

1. An apparatus for low-temperature catalytic gasification of a refinedbiomass fuel, comprising: a fuel hopper (10) to momentarily receiverefined fuel and including a screw feeder (11) to quantitatively supplythe fuel, provided at a lower portion thereof; a catalytic circulatingfluidized-bed gasifier (20) provided in the rear of the fuel hopper(10), and including a shutter connected to the screw feeder (11),provided at a middle portion of the gasifier, and a hot air pipe (21)and a steam pipe (22), provided at a lower portion of the gasifier, adust collector (30) connected to the catalytic circulating fluidized-bedgasifier (20) via a pipe extending from an upper portion of thecatalytic circulating fluidized-bed gasifier (20) to a side wall of anupper portion of the dust collector (30), to collect fly ash; a catalystreformer (40) connected to the dust collector (30) via a pipe extendingfrom the upper portion of the dust collector (30) to a lower portion ofthe catalyst reformer, and including a lower layer of fixed filteradsorbent bed (41) and an upper layer of fluidized catalyst bed (42); aheat exchanger (50) connected to the catalyst reformer (40) via a pipeextending from the upper central portion of the catalyst reformer (40)to a middle portion of the heat exchanger; a tar scrubber (60) disposedin the rear of the heat exchanger (50), and including a tar scrubbingchamber (61), a tar-storing bath (62), and a circulation pump (63) forcirculating tar; and a gas-holder (70) disposed in the rear of the tarscrubber (60).
 2. The apparatus according to claim 1, wherein thecatalytic circulating fluidized-bed gasifier (20) further includes asmall cyclone (23) provided in the upper portion thereof.
 3. Theapparatus according to claim 1, wherein the catalyst reformer (40)further includes a steam sprayer (43) provided at a lower portion of thefixed filter adsorbent bed (41).
 4. The apparatus according to claim 1,wherein the fixed filter adsorbent bed (41) is a cartridge type, andincludes an asbestos filter, particles of alkali earth metal oxide, andparticles of an alkali metal salt, mixed together.
 5. The apparatusaccording to claim 1, wherein the tar-storing bath (62) communicateswith a lower pipe of each of the catalyst reformer (40) and the heatexchanger (50) via tar valves (64) thereof, to collect the generatedtar.
 6. A method of low-temperature catalytic gasification of a refinedbiomass fuel, comprising: a fuel supplying step of supplying a refinedmixture including biomass organic waste, coal, and heavy oil to a middleportion of a gasifier using a screw feeder; a catalytic circulatingfluidized-bed gasification step of drying, volatilizing, low-temperaturecatalytic gasifying, and partially burning the fuel using hot air andsuperheated steam in the presence of a catalyst; a collecting step ofcollecting fly ash in the gas generated in the catalytic circulatingfluidized gasification step; a catalyst reforming step of reforming thegas through a lower layer of fixed adsorbent bed and reformingtar-nitrogen, aromatic-nitrogen, phosphorous and sulfur through an upperlayer of fluidized catalyst bed; a heat exchanging step of cooling thegas to 200° C. or less and transferring condensed liquid to atar-storing bath; a tar scrubbing step of condensing non-converted taror non-condensed liquid to be recovered, and gas stripping the condensedliquid; and a gas-storing step of compressing the gas to be storedtemporarily.
 7. The method according to claim 6, wherein the catalystused in the catalytic circulating fluidized-bed gasification step isselected from the group consisting of natural limestone, lime magnesite,caustic lime, an alkali earth metal including calcium, magnesium orbarium and oxides thereof, an alkali metal including potassium andoxides thereof, alumina, and mixture thereof, each of which is providedin particles or course powders suitable for fluidization.
 8. The methodaccording to claim 6, wherein the catalytic circulating fluidized-bedgasification step further comprises re-circulating a scattered catalystor fuel agglomerate to the catalytic circulating fluidized-bed gasifier(20) through a small cyclone (23).
 9. The method according to claim 6,wherein the catalyst reforming step further comprises spraying steamonto the lower portion of the fixed adsorbent bed (41) to acceleratereformation and prevent the pipe from clogging, so that a reformationtemperature is 650° C. or less.
 10. The method according to claim 6,wherein the catalyst reforming step comprises converting hydrogensulfide into CaS and phosphorous into P_(α)H_(β)S_(γ)Halogen₆₇ (α=1-7,β=0-5, γ=0-7, δ=0-7), to be chemically adsorbed into the fixed adsorbentbed (41).
 11. The method according to claim 6, wherein the fluidizedcatalyst of the fluidized catalyst bed (42) used in the catalystreforming step is a single metal, including Ni, Fe, Co, Mo, Mn, Zr, Ti,Ce, Ru, Rh or Pt, and oxides thereof, or mixtures thereof, whichfunctions to decompose tar by gasification and convert aromatic-nitrogenor HCN into an alkane compound or an alkene compound and NH₃.